“We’re focused on promoting walkable neighborhoods for health benefits,” said Josh Herst, CEO of Front Seat, which created Walkscore. “This makes it easier to understand [that] where people live impacts their daily life.”

Walkscore was launched in 2007 and now is available nationally. The transit scores work in just 40 cities and all those in King County served by Metro and Sound Transit.

Herst acknowledges that many of the most walkable neighborhoods are also the least affordable.

“Today’s demand for highly walkable homes with great access outstrips supply,” he said. “This is what drives the price up. We would support increasing development of walkable neighborhoods.”

A Walkscore adviser, Chris Leinberger, agrees. “If you are in metropolitan Washington, D.C., Boston, San Francisco, Denver, Portland, Chicago or Seattle, you will have about 15 to 20 percent of the region’s housing in walkable urban places versus probably 40 to 50 percent demand. Walkable urban is now the most expensive housing in the metropolitan area.”

Herst said his company added the commute calculator so people can understand how much money they’re spending on transportation.

“People could afford more home if they could live with a single car,” Herst said. “You could walk or bike to work.” He said the transportation cost for an average Seattle household is $686 a month, compared with the regional average of $943 a month.

America’s most walkable city is San Francisco, followed by New York and Boston. Seattle ranks sixth on the list, with a walkable score of 72 out of 100.

According to Walkscore, 57 percent of Seattle residents live in a neighborhood with a score of 70 or above. Most neighborhoods have a score of at least 50, with 14 percent of residents living in car-dependent neighborhoods.

Seattle’s most walkable neighborhood is Pioneer Square, with a score of 99, followed by downtown, 97; First Hill, 96; Belltown, 95; and Roosevelt, 96.

At the bottom of the list is Blue Ridge, with a score of just 32.

Walkscore also scores the walkability of a neighborhood to its proximity to such amenities as grocery stores, schools, restaurants, parks and even bookstores.

The website also has a calculator to show how much of a resident’s average monthly income goes to housing and transportation costs.

According to Walkscore, households in traditional suburbs spend up to 32 percent of their income on transportation costs, while households in walkable areas with good access to public transportation spend as little as 12 percent.